JP2002111105A - Laser diode module device and laser oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a laser diode by preventing the superheating of the diode by reducing the return light returning to the laser diode from an object to be irradiated, and, at the same time, to improve the conversion efficiency by reducing the loss of exciting light when the laser diode is used as the pumping source of a laser diode-excited solid-state laser. SOLUTION: In a laser diode module device which emits a laser beam toward the object to be irradiated, a mask which is arranged to face the laser outputting surface of the laser diode, transmits the laser beam emitted from the laser outputting surface of the diode and made incident on the object to be irradiated, and intercepts the return light made incident on the mask from the object side toward the laser outputting surface, is provided. The laser diode module includes a module having a plurality of laser diodes(LDs), a laser diode unit(LD unit) which has a plurality of laser oscillators formed on a common chip and simultaneously emits a plurality of laser beams, and an LD stack which is constituted by combining a plurality of such LD units by laminating the units upon another. The module also includes a module composed only of one laser diode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode module device used for a laser diode pumped solid-state laser device and the like.

[0002]

2. Description of the Related Art A laser beam emitted from a laser diode (LD) or a laser diode module in which a plurality of laser diodes are integrated is guided to an object to be irradiated, and the object to be processed is subjected to various processings or changes in state. Is known. For example, in a solid-state laser represented by an Nd: YAG laser, a laser diode (LD) is used as an excitation light source instead of a discharge tube.

In this case, a solid-state laser medium (YAG rod) made of Nd: YAG is accommodated in a cooling chamber, and a laser beam enters the chamber through a glass window provided in the cooling chamber. The laser beam entering the chamber enters the solid-state laser medium directly or after being reflected by a reflection plate, and excites active ions (Nd ³⁺ ) doped in the solid-state laser medium. The laser operation is performed using the energy level of the Nd ³⁺ ions excited as described above.

[0004]

The laser beam guided from the laser diode to the solid-state laser medium or the like to be irradiated as described above is not entirely absorbed by the solid-state laser medium, but partially reflected. Returning to the laser diode as light or scattered light is inevitable. This return light,
In particular, return light having the same oscillation frequency component as that of the laser diode is one of the causes of shortening the life of the laser diode by overheating the laser diode. In addition, since this return light is light that is not absorbed by the solid-state laser medium, the return light is nothing but loss of the excitation light and causes a reduction in conversion efficiency.

[0005] The present invention has been made in view of such circumstances, and it is possible to reduce the return light from the object to be irradiated to the laser diode, prevent the laser diode from overheating, and extend the life of the laser diode. A first object of the present invention is to provide a laser diode module device that can reduce the loss of pump light and increase conversion efficiency when used as a pump light source of a laser diode pumped solid-state laser.
The purpose of.

A second object is to provide a laser oscillator using the laser diode module device.

[0007]

According to the present invention, a first object is to provide a laser diode module device for emitting a laser beam toward an object to be irradiated, the laser diode module device being disposed so as to face a laser output surface of a laser diode, and from the laser output surface. The present invention is achieved by a laser diode module device including a mask that passes a laser beam that is emitted and enters the object to be irradiated and blocks return light that is incident from the object to be irradiated toward a laser output surface.

Here, the laser diode module has a plurality of laser diodes (LD), a laser diode unit (LD unit) in which a plurality of laser oscillators are formed on a common chip and a plurality of laser beams are emitted simultaneously. And an LD stack in which a plurality of LD units are stacked and combined. Also, a laser diode including only one laser diode is included. The object to be irradiated can be a solid-state laser medium housed in a chamber, in which case a laser beam enters the chamber through a glass window provided in the chamber.

The mask has an opening through which the laser beam emitted from the LD passes, and a light-shielding portion other than the opening. The light-shielding portion reflects at least light having substantially the same wavelength as the laser oscillation wavelength, thereby receiving return light. It can be returned to the irradiation body (chamber or solid laser medium, etc.) again and used as excitation light. The light shielding portion can be formed by performing a plating process such as gold plating. In this case, the mask can be formed by subjecting at least one surface of the transparent glass plate to a light-shielding process such as gold plating or application of a light-shielding ink except for the opening.

The opening of the mask may be a through hole or a slit formed in a non-translucent plate. The through holes and slits may be tapered so that the diameter increases from the LD (or LD chip) toward the irradiation target. A lens (convex lens) that narrows the spread angle of the laser beam can be attached to these through holes and slits.

By attaching this lens, the spread of the angle at which the laser beam enters the object to be irradiated is reduced,
Laser beam loss is reduced and utilization efficiency is improved. For example, a micro lens and a ball-shaped lens are fixed in the through hole. A cylindrical lens is fixed to the slit. The lens may be a Fresnel lens, and in this case, the light shielding portion and the Fresnel lens can be formed by the same process.

The mounting position of the mask may be not only between the LD (LD chip) and the irradiation target, but also inside the irradiation target.
Further, the glass window of the chamber and the mask may be integrated, and the glass window itself may be used as the mask. Further, the mask may be attached to the laser output surface and integrated with the laser diode module.

The laser beam emitted from the laser diode may be linearly polarized, and the mask may be a polarizing plate having a polarization plane through which the laser beam passes. In this case, since the entire mask may be subjected to a polarization process so as to have the same polarization plane, it is extremely easy to form the mask.

According to the present invention, a second object is to provide a laser medium, an excitation light source for irradiating the laser medium with excitation light, a total reflection mirror provided on each end face side of the laser medium, and an output light. A laser oscillator having a mirror, wherein the laser diode module device according to any one of claims 1 to 12 is used as the excitation light source.

That is, the laser medium is excited by the laser diode module device. In this case, the laser diode module device is desirably used as a lateral excitation type (side excitation type) in which laser is irradiated from the side of the laser medium.

However, there is an end face excitation system in which one end in the axial direction of the laser medium is a total reflection mirror, and a laser emitted from the laser diode module device is made to enter the laser medium from an end face of the total reflection mirror through a condenser lens system. Is also good.
In this case, a total reflection mirror having a large transmittance for the wavelength of the output laser of the laser diode module device and a large reflectance for the wavelength of the laser output from the laser medium is used.

[0017]

1 is a conceptual diagram of an LD-pumped solid-state laser device according to an embodiment of the present invention, FIG. 2 is a diagram showing the LD module device, and FIG. 3 is a cross-sectional view of a chamber including the optical axis of the laser beam. It is.

In FIG. 1, reference numeral 10 denotes a solid-state laser medium (YAG rod) such as Nd: YAG, which has a rod shape with a circular cross section. This solid-state laser medium is accommodated in a cooling chamber 12 having the shape shown in FIG. Chamber 12
A reflector 14 having a U-shaped cross section that is long along the longitudinal direction of the solid-state laser medium 10 is mounted in the inside, and a glass window 16 facing the reflector 14 is provided on one side of the chamber 12.
Is installed. Reflector 14 and glass window 1
The space surrounded by 6 is a cooling liquid flow path 18, and the solid-state laser medium 10 is immersed in the cooling liquid in the cooling liquid flow path 18.

In FIG. 1, reference numeral 20 denotes a laser diode (LD) module device, which includes an LD module 22 and a mask 24.
And formed. Laser output surface 2 of LD module 22
6 faces the glass window 16 of the chamber 12. The mask 24 is located between the laser output surface 26 and the glass window 16. LD in this embodiment
The module 22 has a plurality of LDs along the optical axis 10A of the solid-state laser medium 10, and the LD module 22 has an optical axis 10A along a plane including the optical axis 10A.
A plurality of laser beams 28 that are substantially orthogonal to are emitted.

As shown in FIG. 3, the mask 24 has an opening 30 through which a laser beam 28 passes through an opaque plate having heat resistance.
Is formed. That is, the mask 24 has an opening 30 and a light-shielding portion 32 around the opening. Opening 30 is L
It is a conical small hole formed in a tapered shape that expands in diameter from the D module 22 side toward the glass window 16 side.
These openings 30 are positioned so as to substantially coincide with the light emitting portions of the individual LDs constituting the LD module 22.

A lens 3 for narrowing the spread angle of the laser beam 28 is provided between the mask 24 and the glass window 16.
4 are attached. The lens 34 may be, for example, a cylindrical lens (convex lens), but a convex microlens or a spherical lens may be separately attached to each opening 30. Lens 34 may be a Fresnel lens. When using a Fresnel lens,
By applying a photo process using a photoresist to a transparent glass plate, the Fresnel lens of the opening 30 and the light shielding portion 32 can be formed in the same step.

In the LD module device 20 configured as described above, the laser beam 28 emitted from the LD module 22 passes through the opening 30 of the mask 24 and enters the lens 34. The spread angle of the laser beam 28 is reduced by the lens 34, enters the chamber 12 through the glass window 16, and efficiently enters the solid-state laser medium 10. Therefore, the loss of the laser beam 28 is reduced.

A part of the laser beam 28 entering the chamber 12 is reflected on the surface of the solid-state laser medium 10 or the reflector 14.
And becomes scattered light, and passes through the glass window 16 in the opposite direction. This scattered light reaches the mask 24 and is shielded by the light shielding portion 32 of the mask 24. Therefore, the scattered light is
This prevents the laser diode from being incident on the module 22, protects the laser diode from overheating, and reduces the risk of shortening its life.

On the other hand, the scattered light shielded by the light shielding portion 32 of the mask 24 is again transmitted to the lens 34 and the glass window 16.
Through the chamber 12. Part of the scattered light that has returned to the chamber 12 in this way enters the solid-state laser medium 10 again and is used as excitation light. Therefore, the loss of the excitation light is reduced, and the conversion efficiency is increased.

In FIG. 1, reference numeral 40 denotes a total reflection mirror, and reference numeral 42 denotes an output mirror, which face both end faces of the solid-state laser medium 10. The light reflectance of the output mirror 42 is slightly smaller than that of the total reflection mirror 40. 44 is a driver circuit for driving the LD module 22, and 46 is a control circuit thereof. The pumping light output from the LD module 22 optically pumps the working material (Nd ions) contained in the solid-state laser medium 10 to create a population inversion between the energy levels of the working material.
When the conditions of the total reflection mirror 40 and the output mirror 42 are satisfied, laser oscillation occurs, and a laser beam, that is, a laser oscillation output 48 is output.

In FIG. 1, reference numeral 50 denotes a cooling device,
The cooling liquid is supplied to the second cooling liquid flow path 18 (FIG. 3) and the LD module 22 to cool them. In the embodiment described above, the mask 24 is provided between the LD module 22 and the lens 34 (FIG. 3), but the position of the mask 24 is not limited to this.

For example, the position P _{1 of the} lens 34 shown in FIG.
The position may be a position P ₂ between the lens 34 and the glass window 16, a position P _{3 of} the glass window 16, or a position P ₄ between the glass window 16 and the solid-state laser medium 10. For the position P _3, the glass window 16
The processing of the light shielding portion 32 may be performed directly, or another mask 24 may be bonded to the glass window 16.

[0028]

FIG. 4 is a sectional view of a chamber and an LD module device showing another embodiment. In this embodiment, the LD module device 20A and the chamber 12A are combined and integrated. That is, LD module 2
The laser output surface 26A of 2A enters the coolant flow path 18A from the side surface of the chamber 12A, and a mask 24A serving also as a glass window 16A is disposed in front of the laser output surface 26A. This mask 24
Of course, A has an opening through which the laser beam output from the LD module 22A passes, and a light-shielding portion other than this opening.

According to this embodiment, the size of the apparatus can be reduced. In order to efficiently apply the laser beam emitted from the LD module 22A to the solid-state laser medium 10A, it is possible to fix a lens to the mask 24A or to form a Fresnel lens.

[0030]

Other Embodiments Another embodiment of the mask will be described with reference to FIGS. The mask 24B shown in FIG. 5 has a light shielding portion 32B formed by forming a metal film on a transparent glass substrate except for the opening 30B. This metal film is L
It can be formed of a gold plating layer, a gold vapor deposition film, a metal film, or the like having a thickness that reflects light having a wavelength substantially the same as the oscillation wavelength of the laser beam 28 output from the D module 22.

The mask 24C shown in FIG. 6 is formed by forming a slit through which a laser beam 28 passes on an opaque substrate, and using the slit as an opening 30C. In this case, the opaque substrate itself becomes the light shielding portion 32C.

The mask 24D shown in FIG. 7 is obtained by attaching a lens 34D to the mask 24C shown in FIG. That is, the cylindrical lens 34D was attached and fixed to the opening 30D formed by the slit. 7A is a perspective view of the mask 24D, and FIG. 7B is a side sectional view thereof. According to this embodiment, since the lens 34 shown in FIGS. 1 to 3 can be integrated with the mask 24D, it is suitable for miniaturization of the apparatus.

The mask 24E of FIG. 8 has a small hole which becomes an opening 30E similarly to the mask 24 shown in FIGS. 2 and 3, and its periphery is a light shielding portion 32E. Inside, a circular lens 34E is loaded. This lens 34E may be a micro lens or a ball lens. According to this embodiment, the size of the apparatus can be reduced as in the case of FIG.

The mask 24F shown in FIG. 9 is formed by a polarizing plate. In this case, the laser beam 28F output from the LD module 22 is linearly polarized,
The polarization plane of F is made to coincide with the deflection direction of the laser beam 28F. In FIG. 9, the arrow ← → indicates the direction of deflection.
The laser beam 28F is applied to the chamber 1 shown in FIGS.
2, 12A, and is repeatedly reflected to become reflected light or scattered light. By repeating reflection and scattering, the deflection direction is changed, and the amount of light passing through the mask 24F in the opposite direction is significantly reduced.

[0035]

The invention of claims 1 to 12 is as described above.
Since the return light returning from the irradiation target to the laser diode is shielded by the mask, it is possible to prevent the laser diode from being overheated by the return light and shortening the life of the laser diode. In addition, the return light is returned to the object to be irradiated again by the mask and is effectively used, so that the loss of the laser beam can be reduced and the efficiency can be improved.

According to the thirteenth aspect of the present invention, a laser oscillator using the laser diode module device as an excitation light source can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an LD-pumped solid-state laser device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the LD module device.

FIG. 3 is a sectional view of a chamber.

FIG. 4 is a cross-sectional view showing another embodiment.

FIG. 5 shows another embodiment of the mask.

FIG. 6 shows another embodiment of the mask.

FIG. 7 is a view showing another embodiment of the mask;

FIG. 8 is a view showing another embodiment of the mask.

FIG. 9 shows another embodiment of the mask.

[Explanation of symbols]

 10, 10A solid laser medium 12, 12A chamber 14, 14A reflector 16, 16A glass window 20, 20A LD module device 22, 22A LD module 24, 24A to E mask 26 laser output surface 28, 28F laser beam 30, 30B to E opening part 32, 32B-E light shielding part 34, 34D, 34E lens

Claims (13)

[Claims] 1. A laser diode module device for emitting a laser beam toward an object to be irradiated, wherein the laser diode module device is arranged to face a laser output surface of the laser diode,
A laser diode module device, comprising: a mask for passing a laser beam emitted from a laser output surface and entering the object to be irradiated, and for shielding return light incident from the object side toward the laser output surface. 2. The laser diode module according to claim 1, wherein the object to be irradiated is a solid-state laser medium housed in a chamber, and a laser beam emitted from a laser diode enters the solid-state laser medium through a glass window provided in the chamber. apparatus. 3. The mask has an opening having a size that does not block laser light emitted from the laser output surface, and a light-shielding portion that reflects light having substantially the same wavelength as the laser oscillation wavelength except for the opening. 1 or 2 laser diode module device. 4. The laser diode module device according to claim 3, wherein the mask has a light-shielding treatment applied to at least one surface of the transparent glass plate except for the opening. 5. The laser diode module device according to claim 1, wherein the opening of the mask is formed by a through hole or a slit. 6. The laser diode module device according to claim 5, wherein a lens for narrowing a spread angle of a laser beam emitted from the laser diode is attached to the opening. 7. The laser diode module device according to claim 4, wherein a Fresnel lens is formed in the opening of the mask. 8. The laser diode module device according to claim 2, wherein the mask is disposed between the glass window of the chamber and the laser output surface. 9. The laser diode module device according to claim 2, wherein the mask is provided in the chamber. 10. The laser diode module device according to claim 2, wherein the mask is integrated with the glass window. 11. The laser diode module device according to claim 2, wherein the mask is provided on the laser output surface. 12. A laser beam emitted from a laser output surface is linearly polarized light, and the mask is a polarizing plate having a plane of polarization substantially in the same direction as the laser beam.
Laser diode module device. 13. A laser oscillator comprising: a laser medium; an excitation light source for irradiating the laser medium with excitation light; and a total reflection mirror and an output mirror respectively provided on each end face side of the laser medium. 13. A laser oscillator using the laser diode module device according to claim 1 as an excitation light source.